The effect of exogenous polyamines (cadaverine, putrescine, norspermidine, spermidine, and spermine) on the growth, toxicity, and toxin profile of the dinoflagellate Alexandrium minutum T1 was examined. It was found that cadaverine at concentrations of 0.1-2.0 μmol/L enhanced the growth of A. minutum T1. Putrescine and norspermidine at a low level (0.1 μmol/L) also promoted the algal growth. Spermidine depressed the algal growth. However, the cell toxicity levels of A. minutum T1 cultured with or without cadaverine, putrescine, norspermidine, and spermidine were almost the same. The toxic components of A. minutum T1 were GTXs 1-4 only, and GTXs 1 and 4 were predominant (74.6±7.1%) in all cultures. On the other hand, spermine did not effect the growth of A. minutum T1, though it decreased the cell toxicity and the ratio of GTX 2+GTX 3 (15.0±6.6%).